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From "Dale LaBossiere (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (QUARKS-150) add Valve Predicate
Date Wed, 20 Apr 2016 18:34:25 GMT

     [ https://issues.apache.org/jira/browse/QUARKS-150?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Dale LaBossiere resolved QUARKS-150.
------------------------------------
    Resolution: Fixed

Valve and recipe delivered

> add Valve Predicate
> -------------------
>
>                 Key: QUARKS-150
>                 URL: https://issues.apache.org/jira/browse/QUARKS-150
>             Project: Quarks
>          Issue Type: New Feature
>            Reporter: Dale LaBossiere
>            Assignee: Dale LaBossiere
>
> A Valve Predicate accepts tuples when its state is {@link State#OPEN}, otherwise it rejects
tuples.
> A valve is typically used to dynamically control whether or not
> some downstream tuple processing is enabled.  A decision to change the
> state of the valve may be a result of local analytics or an external
> device command.
> [ fwiw, this is known as a 'Switch' utility operator in IBM Streams ]
> Maybe this belongs in quarks.topology.plumbing/PlumbingStreams, not quarks.analytics.sensors/Filters
like Deadband and Deadtime, since there's not really much "analytic" about it?
> E.g., a Valve might be used to control whether or not logging of tuples is enabled.
> ```
> TStream<JsonObject> stream = ...;
>  
> Valve<JsonObject> valve = new Valve<>(Valve.State.CLOSED);
> stream.filter(valve).sink(someTupleLoggingConsumer);
> // from some analytic or device command handler...
>     valve.setState(Valve.State.OPEN);
> ```



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